Determination of Synchronous Machine Electrical Characteristics by Test

A method of obtaining synchronous machine d and q axis impedances by test as function of frequency of d, q components is presented. The test involves running the machine at reduced speeds, with a line-to-line short circuit between phases, and temporarily applying excitation to produce line-to-line short circuit current at fundamental frequency corresponding to the particular running speed. Records of line-to-line voltages and short circuit current, along with measurement of rotor angle, are processed to yield d and q components of voltages, currents and flux linkages which turn out to be periodic functions of the fundamental frequency plus harmonics. Straight forward Fourier analysis yields the complex values of operational inductances or impedances Ld (j2¿), Lq (j2¿), Zd (j2¿) or Zg (j2¿) where ¿is equal to the speed of the machine at which the tests are conducted.